Due to several advantages of LEDs, such as high luminous efficiency, fast response, no warm-up period, long lifetime, rugged structure, less power consumption, environmentally friendly, small size and so on, many researches on LED bulbs have been conducted. As a result, LED bulbs have gradually replaced conventional incandescent bulbs. FIG. 9 shows a conventional LED bulb 7, which employs a metal base with external threads compatible to the existing standards for lamp bases, wherein the threads have a predetermined pitch between two adjacent threads and have a radius for screwing into to a socket. The LED component used in the bulb has two contacts which are respectively electrically connected to the external threads and the bottom end of the metal base via two metal wires. As such, the LED component can receive electrical current to emit light beams.
However, for fixing the metal wires and preventing a short circuit of the metal wires, the inner surface of the metal base is required to be provided with an insulated material. Furthermore, a transparent case is required to be mounted over the LED component. Manufacturing such an LED bulb involves multiple processing steps, which includes forming a metal base, forming an insulated material on the inner surface of the metal base, mounting an LED component and metal wires, making a transparent case, and mounting the transparent case to the metal base. The complicated manufacturing process results in a high cost of the LED bulb. Since the metal wires requires to be soldered to the metal base, and the metal base requires to be provided with an insulated material, the associated bonding surfaces therebetween should be treated with precision; otherwise, a roughened appearance will result. Furthermore, a bulb using multiple materials will lead to a problem in recycling it and thus depart from the global trend of environmental protection.
Currently, there is another type of lamp base, as shown in FIG. 10, wherein two electrical conductors for connecting with an LED component are made of a conductive plastic, whereas the lamp base 9, which replaces the metal bases commonly used in the existing bulbs, is made of a non-conductive plastic.
Generally, a product using two kinds of plastic, such as a plastic lamp base, can be manufactured in two ways: (1) double injection molding which simultaneously injects two kinds of plastic; (2) insert molding which first forms an object of a first plastic and then places the object in a mold which is then filled with a second plastic. Regarding the technology of double injection molding, it is difficult to control the precision and accuracy of a plastic lamp base, especially the conductors thereof, so that this technology usually leads to a higher cost. Besides, the product yields are poor and thus may cause inefficiency in making the products. As to the technology of insert molding, because the electrical conductors of a plastic lamp base are small in size, they cannot be formed in advance of the insulated body thereof. First, the insulated body is formed by injection molding, wherein some portions of the insulated body are hollowed out and reserved for the electrical conductors. After the insulated body is formed, the hollowed portion can be injected with a second material to form the electrical conductors.
For opening the mold more easily, the conductors of the plastic lamp base are designed in straight shape rather than curved or inclined shape; therefore, they cannot be applied in commonly used Edison Screw Base, including E13, E26 or E27. They can only be applied in a lamp base of bi-pin style. However, due to the plastic pins of the lamp base, which extends downwardly from the bottom of the lamp base, being lack of sufficient structural strength, there is no mature product of this type of lamp base existed on the market so far.
In view of the foregoing, the present invention seeks to provide a plastic lamp base, which can be made by a batch production using basic molding technique, without requiring a complex double injection molding, to promote the production capacity, the product efficiency and yields, and to reduce the manufacturing cost.